Observation of a Λ b 0 $$ {\varLambda}_b^0 $$ − Λ ¯ b 0 $$ {\overline{\varLambda}}_b^0 $$ production asymmetry in proton-proton collisions at s $$ \sqrt{s} $$ = 7 and 8 TeV
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Author(s)
Aaij, R.
Abdelmotteleb, A. S. W.
Abellán Beteta, C.
Ackernley, T.
Adeva, B.
Adinolfi, M.
Afsharnia, H.
Aidala, C. A.
Aiola, S.
Ajaltouni, Z.
Date Issued
October 7, 2021
Publisher
Springer Berlin Heidelberg
Citation
Journal of High Energy Physics. 2021 Oct 07;2021(10):60
Version
Final published version
Abstract
Abstract
This article presents differential measurements of the asymmetry between
Λ
b
0
$$ {\varLambda}_b^0 $$
and
Λ
¯
b
0
$$ {\overline{\varLambda}}_b^0 $$
baryon production rates in proton-proton collisions at centre-of-mass energies of
s
$$ \sqrt{s} $$
= 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated
luminosity of 3 fb−1. The
Λ
b
0
$$ {\varLambda}_b^0 $$
baryons are reconstructed through the inclusive semileptonic decay
Λ
b
0
$$ {\varLambda}_b^0 $$
→
Λ
c
+
$$ {\varLambda}_c^{+} $$
μ−
ν
¯
$$ \overline{\nu} $$
μX. The production asymmetry is measured both in intervals of rapidity in the range 2.15 < y < 4.10 and transverse momentum in 2 < pT < 27 GeV/c. The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both
s
$$ \sqrt{s} $$
= 7 and 8 TeV data, assuming no CP violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in Pythia and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in b-hadron production at LHC energies.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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DOI of Published Version
https://doi.org/10.1007/JHEP10(2021)060
